A C2 domain is usually involved in targeting proteins to cell membranes. Ciliary CC2D2A protein has two C2 domains and an inactive transglutaminase-like peptidase domain (CC2D2A-TGL) []. This entry represents the first C2 domain. CC2D2A (coiled-coil and C2 domain-containing protein 2A) is a component of the tectonic-like complex, a complex localised at the transition zone of primary cilia and acting as a barrier that prevents diffusion of transmembrane proteins between the cilia and plasma membranes []. It is required for ciliogenesis and sonic hedgehog/SHH signalling [].